J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (5): 812-816.DOI: 10.1016/j.jmst.2018.11.014

Special Issue: High Entropy Alloys 2018-2020

• Orginal Article • Previous Articles     Next Articles

Incipient plasticity and activation volume of dislocation nucleation for TiZrNbTaMo high-entropy alloys characterized by nanoindentation

Shao-Ping Wangab, Jian Xua?()   

  1. aShenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016, China
    bUniversity of Chinese Academy of Sciences, 19(A) Yuquan Road, Beijing, 100049, China
  • Received:2018-09-10 Accepted:2018-10-31 Online:2019-05-10 Published:2019-02-20
  • Contact: Xu Jian

Abstract:

With instrumented nanoindentation, incipient plasticity of two as-cast BCC TiZrNbTa and TiZrNbTaMo high-entropy alloys (HEAs) are investigated in terms of pop-in events during loading, to characterize the dislocation behavior in these solid-solution alloys. It is shown that the maximum shear stress (τmax) required for dislocation nucleation is determined to be 1/16-1/12 and 1/18-1/14 of shear modulus for the TiZrNbTa and TiZrNbTaMo HEAs, respectively, which is nearly comparative to the theoretical shear stress of these alloys. The activation volumes of dislocation nucleation the TiZrNbTa and TiZrNbTaMo HEAs are determined to be 1.2b3 for and 1.3b3, respectively, which is substantially irrespective of alloying with Mo. Furthermore, activation volumes of these two HEAs are on the order of cubic burger’s vector and only one-third of the value for TiZrHfNb HEA, suggesting that a heterogeneous nucleation of dislocation took place in a way of direct atom-vacancy exchange, rather than of the cooperative motion of several atoms. These findings reveal the unique feature in deformation of BCC solid-solution complex alloys.

Key words: High-entropy alloys, Nanoindentation, Refractory metals, BCC phase, Incipient plasticity